The present invention relates to preserving ophthalmic formulations or compositions, such as solutions. More particularly it relates to the use of stabilized chlorine dioxide to preserve ophthalmic formulations.
The use of contact lens has become widespread as a replacement for conventional eye glasses because of the improved vision obtained by the wearer or for aesthetic reasons. Contact lenses accumulate microorganisms and cellular debris from the eye. Thus, the lenses must be periodically removed and cleaned to prevent irritation of the eye or infection. Formulations used in lens care must be preserved by some means to interdict introducing microbial contaminants onto contact lenses or into the eye. Disinfecting preparations are part of the regimen indicated for contact lens care.
Numerous ophthalmic formulations have heretofore been used with lenses. The composition of the ophthalmic formulation will often be dictated by the polymeric materials employed in the fabrication of the contact lens. Because of the chemical composition of most ophthalmic formulations, the contact lenses treated, e.g., disinfected, cleaned, soaked, and the like, in such formulations must be rinsed prior to placement in the wearer's eye to prevent irritation of the eye.
Problems have also been encountered in the use of the prior art ophthalmic formulations for the treatment of contact lenses in that such formulations often become contaminated or deteriorate when exposed to the atmosphere once the seal of he formulation container has been broken. Microorganisms and/or other impurities often contaminate the formulation which requires that the formulation be discarded. Thus, there exists a need for aqueous ophthalmic compositions having extended lives. In other words, there is a need for ophthalmic formulations which are effectively preserved without being irritating or otherwise damaging to the eye. It is to such preserved ophthalmic formulations and methods for preserving ophthalmic formulations that the present invention is directed.
Ratcliff U.S. Pat. Nos. 4,696,811 and 4,689,215 disclose the use of stabilized chlorine dioxide for the treatment and prevention of oral disease, for the reduction of malodor, as an anti-plaque agent, an anti-gingivitis and anti-peridontitis agent, as well as a denture soak. These two patents disclose the use of 0.005 percent to 0.02 percent stabilized chlorine dioxide in sterilized water as a contact lens soaking formulation. However, the patents are void of any teaching or suggestion that stabilized chlorine dioxide can be incorporated into an ophthalmic formulation as a preservative for such a formulation. In addition, the patents do not disclose the use of buffer or tonicity components.
Stockel et al U.S. Pat. No. 4,499,077 discloses an antimicrobial composition for soft contact lenses including an oxidizing agent such as an oxyhalogen compound, e.g., stabilized chlorine dioxide, or hydrogen peroxide, and a polymeric germicide, e.g., a quaternary ammonium polymer or an amino and/or imino polymer or salts thereof. Stockel et al U.S. Pat. No. 4,654,208 discloses an antimicrobial composition for contact lenses including an aqueous solution of a germicidal polymeric nitrogen compound and an oxidizing agent, e.g., chlorine dioxide, stabilized chlorine dioxide or hydrogen peroxide, to potentiate the activity of the germicidal polymeric nitrogen compound at low concentrations. The Stockel et al patents characterize the "polymeric germicides" and the "germicidal polymeric nitrogen compounds" as positively charged, nitrogen-containing cationic polymers, such as certain quaternary ammonium polymers and polymeric amino and/or imino compounds, e.g., polydiguanides. Neither of these Stockel et al patents relate to ophthalmic compositions without such positively charged, nitrogen-containing cationic polymers.